Due to their high resolution, high quality images and independence from backlight sources, organic light emitting devices (OLEDs) have attracted considerable attention in display and lighting applications.
An OLED typically comprises an anode layer, a cathode layer and an organic electroluminescent layer positioned between the anode and the cathode layers. Upon application of an electric potential, light is emitted from the device.
The intensity of light emitted by an individual OLED may be inadequate for certain applications in which higher intensity emission is required.
In order to improve the intensity of light, and hence the performance of the device, individual OLEDs may be arranged in stacks.
Such an arrangement is e.g. disclosed in U.S. Pat. No. 6,693,296, wherein an OLED apparatus comprising a substrate and a plurality of OLED devices is disclosed. Each of the plurality of OLED devices includes at least one organic layer extending over an edge of a corresponding spaced apart bottom electrode.
One problem associated with the OLED apparatus of U.S. Pat. No. 6,693,296 is that excess absorption of light may occur within the stack due to the high absorbance of the electrodes. As a result, the overall light intensity may be reduced.
Accordingly, there is a need in the art to provide an OLED device which provides for an enhanced light intensity of the emitted light, especially for use in large-area applications.